Mr Crowley said the change will allow him to “provide a better service for my constituents”

Micheal Martin was dealt a huge blow yesterday after his only MEP defied him and joined a different group in the European Parliament.

Brian Crowley is Fianna Fail’s sole representative in Europe and topped the poll in the Ireland/South constituency.

But yesterday he confirmed he has signed up with the Tory-led European Conservative and Reformist group in direct defiance of his party leader.

In a statement, Mr Crowley said the change will allow him to “provide a better service for my constituents”.

He added: “The ECR Group is a non-federalist, pro-EU group who believes in giving a much stronger say to national governments rather than to EU institutions.

“I also made this move to protect some jobs of Irish staff in Brussels, and not for any personal gain for myself, except my new group will allow me to work more effectively for my constituents in Ireland/South.

“The ECR Group is now the third biggest group in the EU and its priorities include creating long-term jobs and prosperity for member countries, which matches my policy priority.”

The decision is said to have infuriated Mr Martin, who had no idea the move was coming.

Mr Crowley’s status within Fianna Fail is now unclear, as the party itself is still a full member of the Alliance of Liberals and Democrats for Europe.

It said: “We are disappointed with Brian’s personal decision to join the ECR and by doing so align himself to policies and political parties that directly contradict core principles of the Fianna Fail organisation.

“These include the group’s eurosceptic stance and its position on membership of the Eurozone.

“Indeed, a number of the parties in this right-wing grouping stand in direct opposition to Fianna Fail’s Republican ethos and tradition.”

Fine Gael TD Dara Murphy said it showed Mr Martin has lost control of his party at local, national and European level.

He added: “Micheal Martin needs to state whether he supports Brian Crowley’s move to a far-right, eurosceptic group, and he needs to address the pressing issue of his leadership.”

The move is another knock to Fianna Fail after a week dominated by its justice spokesman’s letter to a judge seeking leniency for a drug dealer.